1. Field of the Invention
The invention relates to a display device, and more particularly, to a method of manufacturing a retarder for a three-dimensional image display device.
2. Discussion of the Related Art
Recently, with a user's request for a display device displaying a three-dimensional image having an actual feeling, three-dimensional image display devices have been researched and developed. In general, a stereoscopic image expressing a three-dimension is displayed using a principle of stereovision through eyes. Accordingly, three-dimensional image display devices that display an image of a stereoscopic effect using a binocular disparity due to a separation distance of eyes, e.g., about 65 mm have been suggested. When distinct two-dimensional images of a three-dimensional image display device are viewed to right and left eyes, respectively, the distinct two-dimensional images are transmitted to a brain and are combined to a three-dimensional image having depth effect and reality by the brain. This phenomenon may be referred to as a stereography.
For example, a three-dimensional image display device includes a display panel displaying images, a patterned retarder attached to the outer side of the display panel, and glasses selectively transmitting the images that pass through the patterned retarder from the display panel.
The patterned retarder enables left-eye and right-eye images of two-dimensional images from the display panel to have different phases for each other. For example, the patterned retarder makes the left-eye images left-circularly polarized and the right-eye images right-circularly polarized. By the way, to do this, manufacturing processes of the patterned retarder are very complicated.
FIGS. 1A to 1G are cross-sectional views in steps of a manufacturing method of a patterned retarder according to the related art.
In FIG. 1A, a high molecular substance, which reacts with ultraviolet (UV) light and thus its polymer chains are arranged along a certain direction, is applied to a substrate 10 using a coating apparatus 90 to thereby form a photoalignment layer 20 substantially on an entire surface of the substrate 10. The photoalignment layer 20 includes many disordered polymer chains (not shown).
In FIG. 1B, the substrate 10 including the photoalignment layer 20 thereon is disposed on a drying plate (not shown), which has a surface temperature of 90 degrees of Celsius to 130 degrees of Celsius. A drying process of heating the substrate 10 for several seconds to several minutes is carried out, thereby drying the photoalignment layer 20 and removing a solvent in the photoalignment layer 20.
In FIG. 1C, a first photomask 70 including light-transmitting portions TA and light-blocking portions BA is disposed over the cured photoalignment layer 20. Then, first polarized UV light is irradiated to the cured photoalignment layer 20 through the first photomask 70 to thereby form first alignment areas 21, which are exposed to the first polarized UV light and are selectively aligned along a first direction. That is, the first polarized UV light is irradiated to a portion corresponding to ones of left-eye image pixel rows and right-eye image pixel rows, and the polymer chains (not shown) in the portion are arranged along the first direction. On the other hand, in a portion of the photoalignment layer 20 which is not exposed to the first polarized UV light, the polymer chains (not show) still remain disordered.
Accordingly, the photoalignment layer 20 includes the first alignment areas 21 in which the polymer chains are well arranged along the first direction and non-alignment areas in which the polymer chains are disorderedly arranged due to the selective irradiation of the first polarized UV light.
In FIG. 1D, a second photomask 72 including light-transmitting portions TA and light-blocking portions BA is disposed over the photoalignment layer 20 having the first alignment areas 21 and the non-alignment areas. Here, the blocking portions BA correspond to the first alignment areas 21, and the light-transmitting portions TA correspond to the non-alignment areas. Then, second polarized UV light is irradiated to the photoalignment layer 20 through the second photomask 72 to thereby form second alignment areas 23, which correspond to the light-transmitting portions TA of the second photomask 72 and in which the polymer chains are arranged along a second direction perpendicular to the first direction.
Next, in FIG. 1E, a liquid crystal material that is able to be hardened by UV light, for example, reactive mesogen (RM) is applied to the photoalignment layer 20 including the first and second alignment areas 21 and 23 by a predetermined thickness to thereby form a RM layer 40.
Here, the RM layer 40 includes first phase portions 44 and second phase portions 46 due to the photoalignment layer 20. More particularly, RM molecules 42 of the RM layer 40 corresponding to the first alignment areas 21 are aligned due to the polymer chains arranged along the first direction to thereby form the first phase portions 44, and RM molecules 42 of the RM layer 40 corresponding to the second alignment areas 23 are aligned due to the polymer chains arranged along the second direction to thereby form the second phase portions 46.
In FIG. 1F, non-polarized UV light is irradiated to the RM layer 40 including the first and second phase portions 44 and 46 of FIG. 1E, thereby hardening the RM layer 40.
In FIG. 1G, the substrate 10 including the RM layer 40 hardened by the non-polarized UV light thereon is carried into a curing apparatus 96. The substrate 10 is exposed to an environment including a temperature of 50 degrees of Celsius to 100 degrees of Celsius for several minutes to several ten minutes, and the RM layer 40 hardened by the UV light is cured to be further hardened.
By performing the curing processes such as the UV irradiation and heating, the RM layer 40 includes first phase patterns 50 where the RM molecules 42 are aligned along the first direction and second phase patterns 52 where the RM molecules 42 are aligned along the second direction perpendicular to the first direction. A patterned retarder 1 is completed through the above-mentioned processes.
However, as stated above, the manufacturing processes of the related art patterned retarder 1 are very complicated because of applying a material for the photoalignment layer 20, drying and curing the photoalignment layer 20, two separate exposures using polarized UV lights, applying the RM layer 40, and UV hardening and curing the RM layer 40. This causes an increase in manufacturing costs.